Inflators are used in vehicles to inflate air bags or other inflatables. The inflatables are intended to protect the occupant when a vehicle collision occurs. In connection with a certain class of inflators, their manner of operation depends upon whether or not the collision involving the vehicle is detected as a high impact or a low impact vehicle collision. The air bag of such an inflator is designed to inflate when a special impact to the vehicle occurs or is exceeded. Different vehicle impacts can occur. A low impact collision typically occurs when the impact vehicle is traveling at a relatively low rate of speed. Relatedly, a low impact collision can occur when an impacting vehicle is traveling at relatively low rate of speed when it strikes the impacted vehicle. Conversely, a high impact collision is characterized by one or both of an impacted and impacting vehicle traveling at a relatively high rate of speed. The pressure developed in the air bag need not be the same for the low and high impact collisions. When a high impact collision occurs, it is desirable to inflate the air bag to a relatively high pressure. With a low impact collision, on the other hand, it is desirable to inflate the air bag to a lesser pressure. Relatedly, depending on the age and/or size of the vehicle occupant, it may be advantageous to control the pressure applied by the air bag. For young or small children, it is usually desirable to utilize less pressure in the air bag than when the vehicle occupant is an adult or larger sized individual.
Inflation systems have been proposed that are intended to take into consideration such factors as the degree of vehicle impact, age, and/or size of the vehicle occupant and/or the position of the occupant in the vehicle. In one prior art system, multiple gas generating units for filling an air bag with gas can be selectively activated. More than one such unit is activated when it is desirable to provide relatively increased pressure in the air bag. In another known prior art system, an electrically controlled vent valve, together with two igniters, are used. The vent valve provides a pathway for gases different from the pathway to inflate the air bag. Based on this configuration, if the electronic controller maintains the vent valve closed and fires each of the two igniters, the air bag inflates with 100% of the gas that is generated. On the other hand, for example, if the vent valve is controlled open and only one of the two igniters is fired, the air bag is inflated with a fraction of the maximum possible gas that could be provided.
Although inflator systems have been previously advanced related to controlling the inflation of an air bag, it would be beneficial to incorporate a relatively less complex arrangement that satisfies the key requirements associated with controlling the inflation of an air bag, including relying on components that are already available or are used in such a system, making as few modifications as is necessary to the air bag module and keeping the addition of parts thereto as few as possible.